Hi list!
I was testing mod_substitute and lookaheads. I tested with the simple
setup below (a simple string in an index.html, and a .htaccess file),
and the lookahead yields expected result, the negative lookahead and the
lookbehind have no effect.
The negative lookbehind has a behaviour that I do not understand.
Are only lookahead (?=foo) supported in mod_substitute, and not the
other (negative lookahead, lookbehind and negative lookbehind) ?
Other syntax or did I miss something ?
And as a bonus question, why is the last test ( Substitute
"s/a(?<!m)/Q/" ) changing all letters to 'Q' instead of not changing the
string like the 2nd and the 3rd test ?
Thanks for sharing your insights!
Zimmi
SETUP
index.html :
Llamas are my favorite animals.
.htaccess :
AddOutputFilterByType SUBSTITUTE text/html
# Original string inside an index.html :
# Llamas are my favorite animals.
# 1. Lookahead, OK
# Expected : word 'favorite' changed:
# Llamas are my f4vorite animals.
Substitute "s/a(?=v)/4/"
# 2. Lookbehind, not OK : nothing happens
# Expected : word 'animals' changed:
# Llamas are my favorite animAls.
Substitute "s/a(?<=m)/A/"
# 3. Negative lookahead, not OK : nothing happens:
# Expected : all remaining 'a' changed to '&' except last one in word
'animals':
# Ll&m&s &re my f4vorite &nimals.
Substitute "s/a(?!l)/&/"
# 4. Negative lookbehind, not OK : changes all remaining occurrences of
'a' to 'Q' ? Why ?
# Expected : all remaining 'a' changed to 'Q' except last 'a' in word
'animals'
# and first 'a' in 'Llamas' if not changed by rules before.
Substitute "s/a(?<!m)/Q/"
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